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Thermal conductivity enhanced by the addition of inorganic fillers such as, natural silica has been shown as critical factor improving the erosion performance of silicone rubber filled with micro-sized silica in the inclined plane tracking and erosion test (IPT). In this research, different thermal characteristics of SiR composites filled at 50 w% with natural silica of different median particle sizes (2, 5 and 10 μm) are investigated in both the condensed and gas phases. The thermal conductivity was shown to decrease from 0.5905 W/m.K with 10 μm silica to 0.5230 W/m.K with 2 μm silica, despite the interaction promoted between the 2 μm silica and the polymer. Accordingly, the improvement in the thermal conductivity of SiR by the addition of micro-sized natural silica was elucidated from different perspective than the filler-SiR interaction. The suppression of depolymerization was more evident with 2 μm silica due to the enhanced interaction between the filler and the polymer as indicated by the thermogravimetric and differential thermal analyses., 2020 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), Oct. 18-30, 2020, East Rutherford, New Jersey (Held Virtually)

We present the development and implementation of a novel wavelet shrinkage technique for the retrieval of obscured characteristic resonant signatures in the scattered terahertz (THz) reflectivity of molecular crystals. In this implementation, the wavelet basis functions associated with the absorption features were identified using the second-order total variation of the wavelet coefficients. Additionally, wavelet coefficients at certain scales were modified using the phase function corrections and wavelet hard thresholding. Reconstruction of the original spectra using these modified wavelet coefficients yielded the exact resonant frequencies of the chemicals, which were otherwise unrecognizable in the spectral artifacts of the rough surface scattering. We examined the robustness of this method over controlled levels of rough surface scattering, validated using the Kirchhoff approximation, in spectroscopic targets made from $\alpha $ -lactose monohydrate and 4-aminobenzoic acid (PABA), which have close spectral lines. We successfully retrieved the spectral absorption fingerprints in both specular and off-specular reflection geometries. This technique can be utilized for stand-off material characterization using the THz reflection spectroscopy in uncontrolled environments and potentially can be adopted for other broadband spectroscopic modalities.

The integration of photovoltaic and battery energy storage systems into utility grids is favorable for electricity customers, especially for high consumption load patterns due to the high electricity bill. To increase the annual bill savings and decrease the dependency on the utility grid, a procedure of optimally sizing the PV battery system is presented in this paper. A MATLAB-based code of the genetic algorithm is used to maximize the system self-sufficiency and minimize the discounted payback period while guaranteeing the system profitability. The optimization technique is introduced under the time-of-use tariff structure for residential prosumers in two scenarios. The first introduces a sellback energy price equal to the off-peak energy price, and the second introduces a sellback energy price equal to the on-peak energy price. The economic and technical effects of this optimization are described and analyzed. The effect of PV system capital cost, battery capital cost, and discount rate variations is evaluated by sensitivity analysis. The results indicate that for a sellback price equal to the off-peak price, a minimum discounted payback period can be achieved by installing the maximum PV system size without batteries, and it is reduced to half of its value for a sellback price equal to the on-peak price at the same PV system capacity. For a sellback price equal to the off-peak price, the minimum DPBP of 5.8 years can be achieved by installing a 20 kWp PV system without batteries with 47% self-sufficiency and 2.4 years for a sellback price equal to the on-peak price by installing the same system capacity. The proposed approach highlights that increasing the battery size leads to high self-sufficiency without a considerable decrease in the annual bill savings that encourage customers to invest in the PV battery system.

Carbon fiber reinforced polymer (CFRP) is an anisotropic material with outstanding tensile strength in the axial direction but low compressive strength in the radial direction. In the process of line construction, such as wire crimping and conductor clamping, radial pressure failure and slip failure easily occur. This paper applies finite element analysis (FEA) to the parameters influencing the radial stress and displacement in a CFRP core to research the failure modes of the CFRP core. The selected parameters are the interference of the CFRP core, the friction coefficient between the core and inner wedge, and the angle of the inner wedge. The finite element method is applied to analyze a CFRP core with a self-tightening clamp to find the optimum condition parameters so that the CFRP core experiences neither slip failure nor radial pressure failure. From the study, lower interference and larger friction coefficient and angle lead to lower radial stress. The interference has the largest effect on the mitigation of radial pressure failure. For larger interference, a larger friction coefficient and angle mitigate slip failure. According to the analytic results, an interference between 0.02 mm and 0.025 mm and an angle larger than 3°, coupled with a friction coefficient larger than 0.3, best stop slip failure and radial pressure failure.

For a pulsed laser transmitted in the raised dust from battlefield vehicle movement, the premise of obtaining its transmission properties and anti-jamming method is to acquire the spatial distribution rules of dust mass concentration. In this study, the emission mechanism for vehicle-raised dust in the battlefield environment is analyzed, as well as various influencing factors of the dust emission velocity. A finite volume method (FVM)-based model for simulating the spatial dispersion of dust raised by a certain moving tank is built, and the effects of mass flow rate, traveling speed, wind speed and wind direction on the spatial distribution of dust mass concentration are explored in the battlefield environment. The results show that the raised dust is plume-shaped within the computational domain, and the spatial mass concentration of plume is positively correlated with the mass flow rate. Besides, it is necessary to determine the impact of tank travelling speed on the spatial mass concentration of dust based on the relationship between the travelling speed and the dust mass flow rate. Although front wind reduces the spatial mass concentration of dust plumes, the reduction rate decelerates when the wind speed exceeds 4 m/s. Crosswind leads to the deflection and decreased mass concentration of dust plumes. Under varying wind directions, the variation of crosswind component exerts a more pronounced influence on the spatial mass concentration of dust than that of the front wind component. This study provides a technical support for the further study of near-ground laser weapon system against vehicle dust interference in the battle field.

Carrier velocity modulation by asymmetrical concave quantum barriers to improve the performance of AlGaN-based deep-ultraviolet light emitting diodes has been investigated. The concave structure is realized by inserting a low Al composition AlGaN layer in the barrier, and thus forming a concave region on energy band. The measured device performance shows a significant improvement under 0–250 mA operation current, with the maximum external quantum efficiency and light output power of 1.02% and 8.0 mW, which are more than double (2.32 and 2.35 times) of that for the conventional one, respectively. Simulation confirms that the concave quantum barriers make it possible for electrons to be scattered, which reduce the electron energy before being injected into quantum wells, and thus the capability of quantum wells to capture electrons is enhanced. Meanwhile, the vertical transport of holes within the active region is also enhanced because the asymmetrical setting of the concave layer in the quantum barriers helps holes accelerate under the polarization field, and then get more energy to overcome the barrier.

This paper presents a fluidically loaded microstrip patch antenna on a multi-layered substrate with frequency and polarization reconfigurability in the 2400 MHz band. A square patch loaded at all the corners with short circuited $\lambda _{g}/4$ long stubs is utilized. An arrangement of fluidic channels fabricated by moulding Polydimethylsiloxane (PDMS) with 3D printed mould is incorporated beneath each stub. By injecting or withdrawing distilled water into the channels, variable loads are realized. It exhibits frequency tunable linearly polarized (LP) mode with symmetric loading or circularly polarized (CP) mode with asymmetric loading. The sense of CP can be switched by swapping the loading configuration along the diagonals of the patch. The equivalent circuit for the antenna is presented. A prototype is fabricated and measured. In LP mode, frequency tuning of 7.85% is achieved. The minimum realized gain is 5.67 dBi with cross-polarization (X-pol) isolation $\geq20$ dB. In the CP modes, the overlapping bandwidth for ${\mid }\text{S}_{11}{\mid } \leq -10$ dB and axial ratio $\leq3$ dB (ARBW) is $\geq16$ MHz for both LHCP/RHCP modes. Frequency tuning of 141 MHz (5.76%) is measured in the RHCP mode. The minimum realized gain is 4.86 dBic and total efficiency is >60%.

On-chip optical gas sensors, which use resonant shifts of cavities to detect molecular concentrations, have the advantages of high sensitivity, real-time detection, and compact footprint. However, such sensors are usually limited by a serious cross-sensitivity issue induced by environmental temperature variations. To overcome this limitation, we study a dual-mode graphene-on-microring resonator to accurately measure gas concentrations without suffering from temperature variations. To be specific, the influences of gas-induced graphene’s optical conductivity changes and environmental temperature variations on effective refractive indices of TE0 and TE1 modes in the resonator can be decoupled based on the modal linear independent responses. With this method, we designed a nitrogen dioxide sensor with a sensitivity of 0.02 nm/ppm and a limit of detection of 0.5 ppm. Our study paves the way for developing on-chip optical gas sensors with excellent sensitivity and temperature stability.

In the past two decades, unmanned amphibious robots have proven the most promising and efficient systems ranging from scientific, military, and commercial applications. The applications like monitoring, surveillance, reconnaissance, and military combat operations require platforms to maneuver on challenging, complex, rugged terrains and diverse environments. The recent technological advancements and development in aquatic robotics and mobile robotics have facilitated a more agile, robust, and efficient amphibious robots maneuvering in multiple environments and various terrain profiles. Amphibious robot locomotion inspired by nature, such as amphibians, offers augmented flexibility, improved adaptability, and higher mobility over terrestrial, aquatic, and aerial mediums. In this review, amphibious robots’ locomotion mechanism designed and developed previously are consolidated, systematically The review also analyzes the literature on amphibious robot highlighting the limitations, open research areas, recent key development in this research field. Further development and contributions to amphibious robot locomotion, actuation, and control can be utilized to perform specific missions in sophisticated environments, where tasks are unsafe or hardly feasible for the divers or traditional aquatic and terrestrial robots.

High-contrast transmitarray (HCTA) metasurfaces, named as metalines in this article, a category of lithographically defined on-chip diffractive elements with minimized scattering loss, enables parallel on-chip optical signal processing. While high-performance devices with different functionalities are reported, most of them are static, and their optical functions are fixed after fabrication. However, dynamically tunable metasurfaces are of essential need in many modern optical systems. Here, we employ an inverse design method, combining FDTD parameter sweep with Fourier-optics simulations, to design thermally-controlled varifocal metalenses. Thermal tunability is accomplished through the thermo-optical effect of silicon. Maximum focal length tunability of 12% and 24% are demonstrated for $400~\mu \text{m}$ and $200~\mu \text{m}$ aperture varifocal metalens doublets at the wavelength of $1.55~\mu \text{m}$ , respectively. The focusing efficiency is more than 74% for the whole temperature range. The $400~\mu \text{m}$ and $200~\mu \text{m}$ aperture metalenses are able to concentrate the input beam to spot sizes less than one wavelength and two wavelengths, respectively. This paves the way for dynamically controlled silicon photonics computational chips.

Temperature measurement of an isopropanol-immersed microbottle resonator is demonstrated. The theoretical analysis indicates that the resonance wavelength blue shifts as the increase of temperature, and the temperature sensitivity increases with the decrease of resonator dimension, which are also demonstrated by experimental results. The temperature sensitivity enhancement of up to 4.6 times relative to the sensor in the air is achieved, which could be benefit from the high thermal refraction coefficient of isopropanol. Furthermore, a robust package has also been proposed to make the present sensor more practically.

Lithium-Ion battery packs are an essential component for electric vehicles (EVs). These packs are configured from hundreds of series and parallel connected cells to provide the necessary power and energy for the vehicle. An accurate, adaptable battery management system (BMS) is essential to monitor and control such a large number of cells. Series and parallel connected cells also experience different production and operational conditions, which makes it challenging for the BMS to ensure the safe operation of each individual cell. The main functions of the BMS include battery state estimation, cell balancing, thermal management, and fault diagnosis. Robust estimation of the state of charge (SOC) is crucial for providing the driver with an accurate indication of the remaining range. This paper presents the state of art of battery pack SOC estimation methods along with the impact of cell inconsistency on pack performance and SOC estimation. Cell balancing methods, which are necessary due to cell inconsistencies, are discussed as well. Four categories of pack SOC estimation methods are presented, including individual cell, lumped cell, reference cell, and mean cell and difference estimation methods. The SOC estimation methods are compared in terms of algorithm type, computational load, and engineering effort to help practitioners decide which method best fits their application.

The article presents an analysis of the influence of temperature on the electrical conductivity of composite polyacrylonitrile-polyaniline fibers (PAN/PANI). The fibers are obtained by synthesizing polyaniline directly in the spinning solution of fiber-forming polyacrylonitrile and characterized by X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) methods. Electrical characterization of fibers is performed by current-voltage characteristic. The polarizing voltage of the electrodes in the range from -1 V to 1 V with a speed of 100 mV/sec is changed cyclically and linearly while simultaneously the current is measured. The current-voltage characteristic of the fibers is recorded at various temperatures in the range from -15 °C to 100 °C for 30 min. Based on the measurements, temperature changes in the conductance are determined in constant relative humidity. The current-voltage characteristics of the fibers in the ambient atmosphere with a relative humidity of 38 % are linear and symmetrical, which indicates the electron nature of the conductivity and the ohmic contact of the electrode-fiber. The characteristic of temperature conductance changes is not of a typical shape, it is parabolic. The conductance of the developed PAN/PANI fibers at 22 °C is about $1.50\cdot 10^{\mathrm {-4 { }}}\text{S}$ (6.7 $\text{k}\Omega$ ) and decreases below and above this temperature. The analysis of research results and literature data enables the determination of individual factors affecting changes in conductance of the tested composite fiber.

Non-volatile nanoscale memory devices (such as memristors) have promised to overcome the challenges of scalability and leakage currents of CMOS based memory devices. These novel memories can be fabricated in back-end-of-the-line of any CMOS process. Currently, a lot of research is focused on investigating the benefits of memristors for associative memories. These are Content-Addressable Memories (CAM) in which search based data access takes place. Searching for a particular bit in memristor is time consuming while search in CMOS CAM zone is efficient. To combine the speed and ease of search of CMOS memory and the scalability of memristor memory, we present a novel multibit hybrid CMOS-Memristor Associative Memory Cell. The benefits of such memory cells manifest in on-chip caches - the instruction and data cache, Branch Target Buffer, and Translation Lookaside Buffer. To exemplify the benefit of the cell further, we also simulate the MemCAM as the TLB of an ARM processor and obtained upto 50% decrease in miss rates of Data TLB and upto 93% in that of Instruction TLB. Average speedup of 1.16 was also achieved on various benchmark applications of PARCSEC and MiBench suites.

The all silicon terahertz metasurface with sharp Fano resonance and its sensing applications with high Q factor have been investigated. Such metasurface, composed of periodic grooves, can be fabricated by deep silicon etching on high-resistivity silicon. When the refractive index of the sample changes, the shifted resonance frequency appears and the resonance intensity can be modulated by altering the surface conductivity. The Q characteristics of the metasurface and the applications of graphene sensing are then analyzed and verified. The results indicates that the Q factor of the metasurface can reach 39857, the standard sensitivity is 16042 nm/RIU, and the FOM is 533. Meanwhile, the characteristics of sensing graphene samples (∼1 nm) are very useful for sensing other ultra-thin materials or biomolecules.

This review paper assesses the main approaches in the electrical characterization of advanced MOSFETs towards their future analog and RF applications. Those approaches are shown to be different from the traditionally used ones for the assessment of the device perspectives for digital applications. Based on the original research realized by our group over the last years, advantages and necessity of those techniques will be demonstrated on different study cases of various advanced MOSFETs, such as Fully Depleted Silicon-on-Insulator (FDSOI), FinFETs and NanoWires (NW) in a wide temperature range (from cryogenic, 4 K up to 250°C). A wide frequency band characterization (from DC up to hundred GHz range) will be positioned as a key element enabling a fair device assessment towards analog and RF applications. Importance of the “extrinsic” parasitic elements in the advanced devices is enormous, sometimes even dominating the device performance. Therefrom arises the need for a proper separate extraction and discussion of “intrinsic” versus “extrinsic” parameters.

This research paper represents the analysis and simulation of semi-active suspension using non-linear modeling of the Magneto-Rheological (MR) suspension with consideration of the hysteresis behavior for a quarter car model. The research is based on the assumption that each wheel experiences the same disturbance excitation. Hysteresis is analyzed using Bingham, Dahl’s, and Bouc-Wen models. This research focuses on simulation of passive, Bingham, Dahl, and Bouc-Wen models and analysis for the five road profiles. The desired damping force determines the optimum working conditions based on optimized critical design parameters. An integrated approach towards the numeric design optimization by computational methods has been used to find the optimum working conditions. The critical parameters of MR damper are determined, and multi-objective optimization is performed considering the pole length, piston radius, gap thickness, piston internal radius, piston velocity and coil current. Sensitivity analysis also is performed to identify the sensitive parameter in the MR damper geometry towards the damping force. Analysis shows that gap thickness is the most sensitive geometric parameter of the MR damper. Furthermore, the comparative study of the models for the highest comfort with less overshoot and settling time are executed. The Bouc-Wen model is 36.91% more accurate than passive suspension in terms of damping force requirements, has a 26.16% less overshoot, and 88.31% less settling time. The simulation of the Bouc-Wen model yields the damping force requirement to be 2150N which is 91% of the analytical results.

In this paper, based on the gray value change of reflected light image of porous silicon (PSi) Bragg mirror, a fast and simple biological detection method is proposed. In this method, CdSe/ZnS quantum dots (QDs) are used as markers for refractive index amplification, and digital image method is used for detection. The detection light has the same wavelength as the lowest reflectivity of the edge of the Bragg mirror, and the reflected light radiated on the surface of the Bragg mirror is received by the detector. The theoretical simulation results show that the intensity of the reflected light increases with the increase of the refractive index caused by the biological reaction. According to the experimental results, the average gray value variation increases with the increase of the target DNA concentration and becomes a linear relationship in a certain range. Based on this method, the DNA detection limit is 20.74 pM. The method is low-cost, has a short detection time and can be used in the detection of biosensor microarray.

In this paper, an Ag nanoparticles (AgNPs) modified multimode fiber (MMF) SERS probe prepared based on sol self-assembly method is proposed and fabricated. Different fiber SERS probes (AgNPs-MMF-x, x is the self-assembly time) are obtained by adjusting the self-assembly time. Using rhodamine 6G (R6G) solution as the probe molecule, the far-end performances of the prepared fiber SERS probe are studied, and the AgNPs-MMF-30 probe with obvious advantages in SERS performance is obtained. The limit of detection (LOD) for R6G is as low as 10−9 M, demonstrating the high sensitivity of AgNPs-MMF-30 probe. The enhancement factor (EF) of AgNPs-MMF-30 probe to 10−7 M R6G is about 1.36 × 108. In addition, the AgNPs-MMF-30 probe has an outstanding reproducibility across the entire area with the maximum value of relative standard deviation (RSD) of less than 10.94%. The AgNPs-MMF-30 probe exhibit a long-term stability regarding Raman enhancement of up to 35 days. Importantly, the high-performance AgNPs-MMF-30 probe is further applied as a highly sensitive SERS platform for the trace detection of antibiotic in milk. The fiber SERS probe has the characteristics of fast, effective, remote real-time detection and so on, so it has great potential application in biochemical sensing and food security.

Surface-enhanced Raman spectroscopy (SERS) is an optical technique for molecule identification. However, fabrication of flexible and structured SERS substrates for performance improvement in a facile and cost-effective manner is challenging. In this work, we reported a polytetrafluoroethylene (PTFE)-based flexible SERS substrate by femtosecond laser direct writing (FsLDW) technology. The femtosecond laser-treated PTFE surface is 3D hierarchical micro-/nano-structures, and the structured PTFE-based SERS chip shows excellent performance enhancement. As a result, 10−7 M can be detected, which shows excellent potentials in developing flexible SERS for wearable electronics.

A high-accuracy unsupervised classification model is developed in a multimode self-interference microring resonator (SIMRR). For the SIMRR, there are many whispering gallery modes (WGMs) present. Each of these resonance modes supported by the SIMRR has a different response to different target parameters, so that the SIMRR-based sensor has the super capability to distinguish between multiple components. In the classification model, principal component analysis (PCA) is firstly used to reduce the dimensionality of this multimode sensing information from the SIMRR-based sensor. When the original higher-dimensional data points are projected onto the lower-dimensional data with only the first few principal components, they can be easily categorized into several different types by using density-based spatial clustering of application with noise (DBSCAN) algorithm. As an example, the unsupervised classification method is numerically validated based on a designed three-gas SIMRR-based sensor. The numerical results prove that the classification model can achieve an ultra high classification accuracy for the designed three-gas sensor with more than 60 dB in signal-to-noise ratio.

18650 Lithium-ion batteries are wildly used as power sources for portable electronics because of the standardized format and economical manufacturing cost. However, commercial 18650 cells come in various designs due to the implementation of different protection devices. The current interrupt device and top vent are mandatory protection devices for all commercial 18650 Li-ion batteries. In contrast, the positive temperature coefficient thermistor, bottom vent, and protection circuit are optional protection devices that can be non-installed, installed separately, or combined in commercial 18650 batteries. Four representative commercial 18650 Li-ion batteries were disassembled and compared in terms of the similarities and differences of the protection devices. This paper overviews the working mechanism, advantages, and drawbacks of each protection device. Recommendations on battery selection and potential future trends are then provided.

As a new type of one-dimensional nanomaterial, carbon nanotubes (CNTs) have been used as a chemical sensing material due to their excellent electrical, mechanical and chemical properties. Several recent studies have attempted to obtain an electrochemical sensor based on CNTs, and CNT-based humidity sensors have potential applications in industrial, agricultural and medical fields and in smart wearable electronic devices. Although various CNT-based humidity sensors have been reported, in this work, we investigated the humidity effects in depth and the underlying mechanisms according to CNT type, i.e., semiconducting (s-CNT) and metallic (m-CNT) CNTs, which is determined by the chiral vector during CNT growth. For this purpose, we fabricated CNT-based humidity sensors with highly purified, solution-processed 99% single-walled s-CNT and m-CNT network films bridged by palladium (Pd) electrodes. The fabricated sensors exhibited completely different humidity responses, as denoted by the film resistance as a function of the relative humidity (RH), according to the CNT type. In the s-CNT-based sensor, the resistance tended to decrease as the RH increased, while the m-CNT-based sensor showed the opposite tendency. Based on these results, a humidity sensing mechanism according to the CNT type was proposed in this work. We believe that our findings can serve as design guidelines for CNT-based humidity sensors.

Polymer nanocomposites (PNC) have a great potential for in-situ strain sensing applications in both static and dynamic loading scenarios. These PNCs, having a polymer matrix of polyvinylidene fluoride (PVDF) with a conductive filler of multi-walled carbon nanotubes (MWCNT), have both piezoelectric and piezoresistive characteristics. Generally, this composite would accurately measure either low frequency dynamic strain using piezoresistive characteristic or high frequency dynamic strains using piezoelectric characteristics of the MWCNT/PVDF film sensor. This limits the frequency bands of the strain sensor to either piezoresistive or piezoelectric ranges. In this study, a novel weighted fusion technique, called piezoresistive/piezoelectric fusion (PPF), is proposed to combine both piezoresistive and piezoelectric characteristics to capture wide frequency bands of strain measurements in real time. This fuzzy logic (FL) based method combines the salient features (i.e. piezoresistive and piezoelectric) of the nanocomposite sensor via reasonably accurate models to extend the frequency range over a wider band. The FL determines the weight of each signal based on the error between the estimate and actual measurements. These weights indicate the contribution of each signal to the final fused measurement. The fuzzy inference system (FIS) was developed using both optimization and data clustering techniques. In addition, type-2 FIS was utilized to overcome the model’s uncertainty limitations. The developed PPF methods were verified with experimental data at different dynamic frequencies that were obtained from existing literature. The fused measurements of the MWCNT/PVDF were found to correlate very well with the actual strain and a high degree of accuracy was achieved by the subtractive clustering PPF’s FISs algorithm.

This paper describes the influence of Longitudinal Corner Effect (LCE effect) and PArallel Connection of Metal–Oxide–Semiconductor Field-Effect Transistors (MOSFETs) with Different Channel Lengths Effect (PAMDLE effect) of Diamond (hexagonal gate shape) MOSFET in different Complementary Metal-Oxide-Semiconductor (CMOS) Integrated Circuits (ICs) technologies (180nm-Bulk and $1\mu \text{m}$ -Silicon-On-Insulator, SOI) and in a wide range of high-temperatures (from 300K to 573K). The results have shown (average gains of Diamond MOSFET in relation to standard MOSFET: 60% for saturation drain current, 51% for transconductance, 10% for transconductance-over-drain current ratio etc.) that LCE and PAMDLE effects tend to be similar for CMOS ICs technological nodes used and the different high temperatures. Therefore, we can conclude, for the first time, that LCE and PAMDLE effects are kept active in different CMOS ICs technological nodes and when the Diamond MOSFET is exposed at high temperatures.

The flow pattern is of great significance for calculating boiling heat transfer and two phase flow pressure drop, and there is no uniform flow pattern diagram for the evaporative cooling system. This paper has carried out experimental research on the flow pattern in the liquid box of the surface-mounted evaporative cooling system and establish a mathematical prediction model of flow pattern transition. The experimental results show that the flow patterns are mainly bubble flow, churn flow, and misty flow in the liquid box of the surface-mounted evaporative cooling system under different thermal loads. By comparing observed flow patterns with existing flow pattern diagrams, it can be found that the existing flow pattern diagrams are not suitable for the flow pattern division of surface-mounted evaporative cooling system. A new flow pattern diagram is proposed based on the change of interfacial area concentration in the liquid box. The prediction results of the new flow pattern diagram are in good agreement with the experimental data, which provides valuable insights into the flow pattern and paves the way for further boiling heat transfer calculation of surface-mounted evaporative cooling system.

We investigated the impact of a sulfur passivation (S-passivation) process step on carrier transport properties of surface-channel In0.7Ga0.3As quantum-well (QW) Metal-Oxide-Semiconductor Field-Effect-Transistors (MOSFETs) with source/drain (S/D) regrowth contacts. To do so, we fabricated long-channel In0.7Ga0.3As QW MOSFETs with and without (NH4)2S treatment prior to a deposition of Al2O3/HfO2 = 1-nm/3-nm by atomic-layer-deposition (ALD). The devices with S-passivation exhibited a lower value of subthreshold-swing (S) = 74 mV/decade and more positive shift in the threshold voltage ( $\text{V}_{\mathrm{ T}}$ ) than those without S-passivation. From the perspective of carrier transport, S-passivated devices displayed excellent effective mobility ( $\mu _{eff}$ ) in excess of 6,300 cm2/ $\text{V}\cdot \text{s}$ at 300 K. It turned out that the improvement of $\mu _{eff}$ was attributed to reduced Coulombic and surface-roughness scatterings. Using a conductance method, a fairly small value of interface trap density $({\mathrm{ D}}_{\mathrm{ it}}) = 1.56 \times 10^{12}$ cm $^{-2}$ eV $^{-1}$ was obtained for the devices with S-passivation, which was effective in mitigating the Coulombic scattering at the interface between the high-k dielectric layer and the In0.7Ga0.3As surface-channel layer.

The nonlinear optical materials with small footprint, low operating energy, ultrafast and large nonlinear optical response are highly required for the signal processing. Here, we investigated the broadband optical nonlinear response of the triangular gold nanoplates on indium tin oxide (ITO) coated glass, and obtained a large optical nonlinear enhancement at its localized surface plasmon resonance (LSPR) region at the wavelength of 780 nm, far from the ENZ (epsilon-near-zero) region of ITO. The measured nonlinear refractive index and nonlinear absorption coefficient can reach up to 8.39×10-15 m2/W and 5.81×10-8 m/W, respectively. The experimental results highlight the noble metals’ potential for nonlinear optics and nanophotonics.

The low RCS level out of operating band is urgent for radome while keeping its communication window. To solve this problem, we propose a frequency selective rasorber (FSR) that exhibits a pass-band between two absorption bands in this paper. The surface currents on a finite metallic wire media is analyzed firstly to elaborate transverse standing waves mechanism. High-efficiency and broadband absorption can be achieved by loading lumped resistors at high amplitude of standing waves. By delicately engineering the transverse standing waves versus frequency, a transparent window can be opened within an absorption wideband and it can be modulated by adjusting structural parameters. The transparent window centered around 10.0 GHz in the absorption band from 5.8 GHz to 18.0 GHz. Prototypes were fabricated and measured. Both the simulated and measured results show that for both x- and y-polarized waves, insertion loss of the transparent window at 9.85 GHz is below 0.2 dB while the absorption is above 90% in the two sidebands of 5.8-7.8 GHz and 11.8-18.0 GHz. Furthermore, the rasorber can also work well under oblique incidence angles up to 45 degrees. This work may find wide applications in electromagnetic compatibility, stealthy radomes, etc.

We present the machine learning inspired design of two types of GaN zero contrast subwavelength gratings (SWGs): a polynomial-shaped grating and, for reference, a conventional rectangular grating, using the differential evolution algorithm to optimize the designs for high broadband reflectivity and separately for large fabrication tolerance. Two wavelength regimes with 500 nm and 1.55 μm center wavelengths (λcenter) are investigated. Our results indicate that both polynomial and rectangular grating designs can achieve comparable stopband widths of 170 nm (Δλ) for 500 nm (Δλ/λcenter = 34%). For the 1.55 μm center wavelength, the 482 nm (Δλ/λcenter = 31%) stopband width of the polynomial grating is slightly less than that of the rectangular grating at 498 nm (Δλ/λcenter = 32%). We also demonstrate design for enhanced fabrication tolerance while placing a minimum constraint on the stopband width. Our results show the rectangular grating exhibits slightly higher fabrication tolerances for grating parameters than the polynomial-shaped grating in general. This work also outlines the technique we have adopted for the inverse design of these gratings.

This paper presents the calibration of the novel kinetic velocity model (KVM) in the drift-diffusion (DD) transport approach, which can account for the ballistic effect in short-channel devices. The KVM considers a thermionic emission limit and a free carrier acceleration limit for the mobility. We develop a methodology to extract the parameters for the KVM and for the high-field saturation velocity model for SiGe nanowires over the whole mole fraction range. The calibrated DD simulations with KVM show good agreement with Boltzmann transport equation results in terms of on-state current and carrier-weighted velocity distribution over a wide range of gate lengths for both linear and saturation regimes.

This article provides a tutorial on the dynamic modeling of continuum robots. Continuum robots (CRs) have gained popularity in recent years due to their flexible backbone structure. Modeling and control of CRs motivate accurate and efficient dynamic models. Such models will enable simulation of dynamic behavior, improved structural design, and the development of dynamics-based control systems for CRs. As a unified underlying approach, the Cosserat rod-based modeling of tendon-driven CRs is used as the basis of the modeling techniques discussed in this paper. In addition to conventional continuum robot assemblies, new and emerging assemblies such as tendon-bent concentric tube and co-operative robots are also considered. The governing equations of motion for conventional CRs are first summarized and then extended for other tendon-driven CRs. This tutorial also contributes to developing a MATLAB code package for simulation of the dynamic response of these robots. The presented method and codes provide a useful and compact resource for readers and can be used for further development of tendon-driven continuum robots.

1/f noise provides essential information on the interface trapping effect as well as the scattering mechanism in transistors. In this work, a systematic 1/f noise study has been carried out on the recessed-gate enhancement-mode (E-mode) GaN MOS-HEMTs under electrical and thermal stress together with the depletion-mode (D-mode) counterpart. Low-frequency (1–1000 Hz) measurement has been performed at room (25 °C) and elevated (100 °C) temperatures at different carrier densities at the drain bias of 2 V and 10 V. The results show the E-mode device has much better noise characteristics under high voltage and high temperature compared with the D-mode counterpart. Moreover, charge-noise model reveals that the improved noise behavior of the E-mode device at high density and high drain bias at 100 °C originating from the energy band alignment at high biases, where the D-mode device suffers from extra charge trapping scattering in the gate edge near the gate-to-drain access region.

In this study, a high-performance orbital angular momentum (OAM) beam is designed, analyzed and experimented using a 1-bit programmable metasurface. OAM as a novel technology is investigated systematically in this paper. Moreover, this study is motivated by the application requirements of real-time controllable communication. The proposed programmable metasurface comprises 1-bit phase modulation units with only two phase states, which is evolved from an electromagnetic surface composed of 360° continuous phase units based on the principle of 1-bit phase quantization. First, the necessity and feasibility of developing the OAM beam based on 1-bit programmable metasurface are studied. Then, qualitative analysis of OAM beams is conducted on different OAM modes and phase modulation elements. Next, the quantitative indexes of OAM beams such as the peak gain in far-field, the divergence angle of main lobe, and circumferential symmetry in azimuth planes are systematically analyzed through a survey of key factors. It is noteworthy that this analysis provides a powerful research basis to achieve an excellent OAM beam with the adjustable function. Thereafter, an active reflective programmable metasurface with 48×48 elements is fabricated to verify the feasibility of developing an OAM beam using a 1-bit element. The experimental and simulation results are in good agreement. Furthermore, a high gain OAM beam with a narrow divergence angle is realized by using the large-scale 1-bit programmable metasurface. Notably, a high-gain beam and an OAM beam can be both generated and can converted into each other, which lays the foundation to achieve the OAM beam with the function of real time dynamic control in future.

This article introduces a dynamic semiempirical model that predicts the degradation of a proton exchange membrane fuel cell (PEMFC) by introducing time-based terms in the model. The concentration voltage drop is calculated using a new statistical equation based on the load current and working time, whereas the ohmic and activation voltage drops are updated using time-based equations borrowed from the existing literature. Furthermore, the developed model calculates the membrane water content in the PEMFC, which indicates the membrane hydration state and indirectly diagnoses the flooding and drying faults. Moreover, the model parameters are optimized using a recently developed butterfly optimization algorithm. The model is simple and has a short runtime; therefore, it is suitable for monitoring. Voltage degradation under various loading currents was observed for long working hours. The obtained results indicate a significant degradation in PEMFC performance. Therefore, the proposed model is also useful for prognostics and fault diagnosis.

Fiber-optic Cherenkov radiation (FOCR) is a promising nonlinear process that is widely used for nonlinear wavelength conversion. In this study, an all-fiber 920-nm femtosecond pulse source is experimentally demonstrated by using Cherenkov radiation. The 4-nJ 150-fs 1550-nm amplified seed pulse source ensures highly efficient 920-nm pulse generation. Cherenkov radiation is stimulated by inputting the high-energy ultrashort pulse to a highly nonlinear fiber. The dispersion values of the highly nonlinear fiber (HNLF) are carefully chosen to generate CR pulses at 920 nm. The generated pulse has a 150-pJ single pulse energy and a 232-fs pulse duration. The typical 30-nm bandwidth can support a sub-50-fs transform-limited pulse duration. The pump current can be adjusted to tune the central wavelength of the pulse source over 905–930 nm. This very simple approach can generate 920-nm femtosecond pulses. The wavelength range is useful for a wide range of applications, such as two-photon microscopy (TPM) in bio-imaging and so on.

How to integrate the temporal and spatial continuity information, when designing the video texture description operator, is crucial to realize video face recognition and facilitate video analysis and understanding, however, it has still yet to be properly addressed. In this paper, a novel video face recognition algorithm is proposed based on an aggregated local spatial-temporal descriptor (ST-VLAD), followed by a novel Fisher Criterion-based weight-learning method, which portrays the local information of the video more accurately, therefore largely improving the representation ability of description vectors. The proposed descriptor was tested on two representative databases, Honda/UCSD and YouTube Face database, achieving accuracies of 89.7% and 87.3%, respectively. The proposed method greatly outperformed the other existing state-of-art methods, suggesting a potential broad utility in the field of video face recognition.

A surface plasmon resonance (SPR) based photonic crystal fiber (PCF) sensor having a milled microchannel, and an open D-channel has been proposed in this paper. The sensor shows good functionality in the wide sensing range of 1.14-1.36 Refractive Index Units (RIU) of the analyte, having the capability to detect low refractive index (RI). The Finite Element Method (FEM) based numerical investigations dictate that the proposed sensor has been able to gain a maximum wavelength sensitivity of 53,800 nm/RIU according to the wavelength interrogation technique. The amplitude interrogations show that the sensor has the highest amplitude sensitivity of 328 RIU-1. The highest FOM (Figure of Merit) has been found to be 105 RIU-1. The sensor evinces a minimum wavelength resolution of $1.86\times 10 ^{-6}$ RIU, which secures high detection accuracy. A circular perfectly matched layer (PML) is implemented in the sensor's outermost layer as a boundary condition to absorb surface radiations. Gold is the plasmonic metal, while TiO2 acts as the adhesive layer for gold attachment on silica. Due to the high sensitivity with a broad range of analyte detection, the sensor is well suited for practical biochemical detection purposes.

In this paper, a novel noise adaptive moving horizon estimation (NAMHE) method is proposed to improve the accuracy of state of charge(SOC) estimation of Li-ion batteries under the unknown noise conditions. Specifically, based on the maximum likelihood principle, the unknown statistical characteristics of the noises can be estimated to modify the recurrence expression of the NAMHE. Then, the SOC estimation algorithm is designed by combining the equivalent circuit model and the proposed NAMHE. Furthermore, the convergence of the estimation error expectation is obtained for the NAMHE algorithm. Finally, the simulation results clarify that the SOC estimation error under the different unknown noise conditions can be effectively reduced by the proposed method, compared with the traditional MHE method.

In the reconstruction of cylindrical phase-only hologram (POH), speckle noise caused by the addition of random phase is rarely discussed. Although some speckle noise suppression algorithms have been proposed for planar POH, it does not work well if they are directly applied to cylindrical POH. To solve this issue, the cylindrical self-diffraction iteration (CSDI) algorithm is proposed. This is an iteration algorithm based on the cylindrical self-diffraction model which is a special case of the cylindrical backward-propagation model at a limit condition. Simulation results show that CSDI can suppress speckle noise and improve the quality of reconstructed images significantly. Furthermore, the proposed CSDI algorithm outperforms conventional algorithms, which work well in planar POH and are directly applied to cylindrical POH, in suppressing speckle noise for cylindrical POH. To our best knowledge, the models of cylindrical backward-propagation and cylindrical self-diffraction as well as the concept of CSDI are firstly proposed and applied to speckle suppression of cylindrical POH.

For dynamic three-dimensional (3-D) surface reconstruction of continuously deformed objects, an efficient method employing one fringe pattern is proposed. First, a two-dimensional wavelet transform profilometry (2-D WTP) employing an improved cost function is adopted to obtain the wrapped phase, which has the better noise suppression ability. Then, a new 3-D phase unwrapping algorithm is introduced to obtain the unwrapped phase, which includes four steps. a) A new 3-D residues recognition method is proposed. b) A 3-D branch cut construction algorithm based on an improved GA is proposed. c) A 3-D phase derivative variance quality map is established. d) A 3-D flood filling phase unwrapping algorithm guided by 3-D quality map avoiding 3-D branch cut (3-D FGQAB) is introduced to obtain the unwrapped phase. Simulation and experimental comparisons are carried out, the results show that the proposed method can be applied to dynamic 3-D reconstruction of the continuously deformed objects.

In this work, we apply a molecular dynamics simulation of Ag-nanoparticle-doped epoxy resin to analyze in depth the micro-mechanisms in this nanodielectric. The simulation results show that when Ag nanoparticles with a radius of 10Å are used as dopants, the periodically arranged atoms in a ~4.5-Å-thick surface layer of the nanoparticles have become amorphous. This modification of the interface depends on temperature and nanoparticle size and leads to an interface polarization layer that changes the relative permittivity of the epoxy matrix. Moreover, a simulation indicates that doping with Ag nanoparticles can improve certain thermal and mechanical properties. However, the interface properties have little effect on the thermal and mechanical properties of nanodielectrics, which may depend only on the thermal and mechanical properties of the doped material itself, the doping concentration, or the microstructure of the nanodielectrics. The innovation of this article lies in the study of the microstructure characteristics of the nanodielectric and the changes of some key physical parameters at the nanoscale by means of molecular simulation. It provides a more efficient research idea for the traditional, experimental-based nanodielectric field. Our results may help in the analysis of nanodielectrics and insulating materials, and they suggest that doping with Ag nanoparticles may improve the thermal and mechanical performance of dielectrics.

We demonstrate an interactive holographic display system for real-time drawing and erasing of 3D point-cloud images. This system detects the position of the observer’s fingertip with a motion sensor, which it uses to calculate the complex amplitude distribution for the hologram. Because the calculated distribution is added to or subtracted from the complex amplitude distribution of the previous frame, the calculation time per frame is independent of the number of points comprising the 3D point cloud. Then, the system can quickly update the hologram even when the number of points comprising the 3D point cloud is increased. Because the 3D point-cloud image reconstructed from the calculated hologram is projected at the same position as the observer’s fingertip with almost no latency, the system can draw and erase a 3D point-cloud image through interactions with the observer’s fingertip. We experimentally confirmed that the system successfully draws and erases a 3D point-cloud image.

In this article, we report robust vector soliton bunches arising in a passively mode-locked fiber laser based on carbon nanotube (CNT). By introducing a polarization-route-assisted module (PRAM) and finely adjusting the cavity birefringence, the soliton bunches can be flexibly manipulated to operate with controllable soliton numbers and positions. Moreover, the potential bandwidth resource provided by the concept of soliton bunches for the ease of breaks a new path for the enhancement of data-carrying capacity. Our research is helpful to extend the theory of vector soliton dynamics in fiber lasers and promotes the promising application in optical communication systems.

A phase unwrapping algorithm assisted by light field without additional time coding is proposed, which can be used in various aspects of optical imaging and metrology. The phase consistency between the light field and the industrial camera is the sticking point to convert the angular resolution of the light field into the order of phase. By virtue of the angle information recorded by the light field, the correct order can be uniquely determined from several candidate orders without confusion in the measurement volume. The mandatory requirements for system fixation and pre-calibration and the connection between the light field and industrial camera are prerequisites for order uniqueness. The mapping relationship established by the phase implies coordinate conversion, lens distortion and other factors, thus providing a high degree of stability for the transmission of phase order information. The achieved results demonstrate that our method is robust and can be taken as an effective tool for means of phase unwrapping.

AlGaN/GaN-Si based MIS-HEMTs are considered as the popular candidates for application in the 5G communication system due to their competitive characteristics and low cost. Ohmic contact, as an important fabrication process, significantly affects the performance of the device. In this study, the ohmic contact process, including the SiN passivation layer etching, surface treatment, and barrier layer etching, was studied in detail in order to effectively optimize the device performance. It is observed that the sample with the SiN passivation layer etched by the magnetic neutral loop discharge (NLD) resulted in a lower contact resistance as compared to the reaction ion etching (RIE). The sample surface treated with the O plasma and pickled in the HCl:H2O = 1:10 liquid could effectively remove the pollutants and oxides from the surface, thus, correspondingly presenting a lower ohmic contact resistance as compared to the N2 plasma. Meanwhile, an optimum etching depth was developed with the ICP process for 6 min with an etching speed of 1.6 nm/min. A contact resistance of $0.76~\Omega \cdot \text {mm}$ and square resistance of 274.63 ohm/sq were observed under the above-mentioned optimized ohmic contact process. The AlGaN/GaN-Si MIS-HEMT with gate length of $0.5~\mu \text{m}$ , gate-source space of $1~\mu \text{m}$ , gate-drain space of $2.5~\mu \text{m}$ , and gate width of $100~\mu \text{m}$ was fabricated using the optimized process. A saturation current density of 794.30 mA/mm and the maximum transconductance of 16.86 mS were observed. The findings in this study provide the experimental basis for the manufacturing of AlGaN/GaN-Si based MIS-HEMTs for RF applications.

In this manuscript, a method of generating an ultra-long optical needle (depth-to-width ratio 37.5:1) is proposed and demonstrated by focusing an azimuthally polarized beam. In theory, the action mechanism between the incident beam and the amplitude modulation element, the spiral phase modulation element, the focusing lens were studied based on the Richards and Wolf's theory. The relationship between the intensity distribution of the optical needle and the structure parameter of the element were obtained, thus leading to the complete design model and design standard. In experiment, the annular amplitude modulation element and spiral phase modulation element were fabricated by lithography. The optical needle was obtained based on a custom-designed optical setup in our laboratory. The optical system consists of an annular aperture (3.9-mm inner diameter, 80-μm annular width), a spiral phase plate (topological charge of 1), and an objective lens with numerical aperture of 0.95. Finally, an optical needle with a subwavelength size (0.416λ) and an ultra-long depth of focus (15.6λ) was obtained, showing an excellent agreement with our theoretical model.

A low-profile and wideband transmissive polarization rotator is proposed in this article. The wideband performance is accomplished by utilizing a curved bowtie resonator. The proposed wideband design exhibits a simulated bandwidth of 129.07% for at least 90% cross-transmission coefficient. The operating bandwidth is from 22.8 GHz to 105.8 GHz and the structure thickness is $0.082~\lambda _{\mathrm {max}}$ , where $\lambda _{\mathrm {max}}$ is the free-space wavelength at the lowest operating frequency. A comparison with previously reported wideband polarization rotator designs is performed to highlight the notability of the proposed design regarding the wideband performance and structure thickness. In addition, in-band notches are utilized within the wide operating band to accomplish a transmissive polarization rotator with multiple operating bands. Single and double notches are employed to achieve polarization rotator designs with dual- and tri-band of operation, respectively. Moreover, the proposed multiband technique enables bandwidth adjustment. The prototype is fabricated and experimentally studied and is found to be highly correlated to the numerical estimation.

A suspended thin-film lithium-niobate-on-insulator nano-waveguide (NanoLN) is designed, and tunable mid-infrared dispersive wave generation of high-efficiency and broadband is numerically studied on this designed platform. By hollowing out the silicon dioxide substrate between the NanoLN core and silicon wafer, the loss issue induced by mode leaking at mid-infrared region is eliminated. The second zero-dispersion wavelength of the suspended NanoLN is tailored to locate around 2 $\mu \text{m}$ wavelength, so that mode-locked fiber laser pump sources in this waveband can be conveniently leveraged to generate dispersive wave beyond 3 $\mu \text{m}$ wavelength. We show that dispersive wave at 3.16 $\mu \text{m}$ with high conversion efficiency up to 36.26% and bandwidth (at −10 dB level) of ~ 471 nm can be achieved at the pump pulse energy of 0.23 nJ. The central wavelength of the dispersive wave can be flexibly tuned up to 5 $\mu \text{m}$ with a maximum −10 dB bandwidth of $\sim ~2~\mu \text{m}$ by lithographic control of the waveguide geometry, which is naturally at the expense of degraded conversion efficiency. Our results show the suspended NanoLN can provide a versatile chip-scale platform for cost-effective mid-infrared targetable, broadband, and coherent sources generation. Using fiber laser pump sources gives the advantages of compactness, free-maintenance, and long-term stability, which suit field applications.

Topological index is a numerical descriptor of a molecule, based on a certain topological feature of the corresponding molecular graph, it is found that there is a strong correlation between the properties of chemical compounds and their molecular structure. In the other side, titania nanotube is a well-known semiconductor and has numerous technological applications such as biomedical devices, dye-sensitized solar cells, and etc. In this paper, the second Hyper-Zagreb index and their coindex of Titania nanotubes have been computed. Furthermore, strong correlation coefficients between second Hyper-Zagreb index and some physicochemical properties such as Density (DENS), Molar volume (MV), Acentric factor (Acenfac) and Entropy (S) have been Appeared.